Rotate HDR picture from background with Blender Render/Internal, not Cycles
You can rotate the HDR background image in Blender Render (Internal render engine) by using the Mapping Size property in the Texture panel.  Use the X axis if you have a normal setup and increment or decrement from the default 1.00 setting.  You range of change is limited to +/- .9 before you will receive distortion.